(Adapted from applicant's abstract): This is one half of a proposed multicenter study. The specific goals of this proposed are: a) to compare the effects of chlorimipramine (CMI), behavior therapy (BT), CMI+BT, and pill placebo for symptoms of obsessive-compulsive disorder (OCD); and b) to compare the relapse rates for the different groups after discontinuation of treatment. This proposal is a collaboration between pharmacologically and behaviorally oriented research programs. Each center will enter 76 patients, randomized in a 12-week trial with the following groups: CMI alone, BT alone, CMI + BT, and placebo pill. After week 12, responders will be tapered and/or discontinued from treatments and followed blind to former treatment status for 12 weeks. Medication will be tapered within three weeks.